barmitzvah shoot

If at all possible, it might be useful for you to try to attend a Bar Mitzvah as an observer before you do the shoot. At least, you would have some idea as to what happens.

Regardless, if I were in your shoes, even though you have been up front with the client as to your lack of experience and it does not seem to be a problem for them, I would still decline the job.
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Don